I have the problem that NCR officers have just started to attack me for no reason. I am still able to trick non named NPC's with a disguise however all named NPC's attack me immediately on site. As far as I can tell there was no real reason for this. My faction standing was good. No idea why this started to happen. It just began after meeting with Benny in the strip.

Intel core duo T8100 2.10 Ghz
4 GB Ram
Windows 7 32-bit (legitimate)
Steam version
Installed:
Old World Blues
Dead Money
Honest Hearts
No Mods